As is well-known, the function of a telecommunications network is to establish a connection between a calling station and a called station. Once such a connection is established, then the calling and called stations may begin to exchange signals, for example, voice signals, with one another. Typically, elements in the connection, or path, operate to perform a particular function in the transmission of such signals. For example, an echo canceler, which is typically contained in a network connection, operates to cancel out of speech signals that it receives so-called echo signals to prevent the latter signals from being returned to the source of the speech signals, i.e., a telephone station set.
As another example, other network elements contained in a connection may operate to perform a different function on signals as they pass through the network. For example, one such element may be arranged to selectively raise the level of speech signals residing in the baseband, e.g., 100 Hz through 300 Hz, as disclosed in copending U.S. patent application of Ser. No. 07/620997 filed on Dec. 3, 1990 on behalf of D.O. Bowker et al. and allowed Sep. 21, 1992.
Thus, the transmission of signals through a network connection may be enhanced by subjecting such signals to a number of different signal processing functions. In certain situations, however, the quality of such signals could be degraded if they were subjected more than once to the same signal processing function. For example, if the function that selectively raises the level of baseband speech signals were applied more than once to such signals, then the level of the baseband signals relative to the remainder of the band would be exceedingly high, thereby possibly distorting such signals before they are delivered to a receiving telephone station set. As another example, and as mentioned above, it si advantageous to pass speech signals through an echo cancellation process to remove echo signals. However, passing speech signals through additional echo cancelers that may be in a connection would not improve the quality of such signals. In fact, doing so could degrade the quality of speech signals, since the level of so-called quantization distortion, which is a by-product of the echo cancellation process, would increase.
Accordingly, there appears to be a need for controlling the number of items that signals, or the like, may be subjected to a particular network function.